An apparatus for machining tube ends, in particular for cutting threads in a tubular workpiece rotating about an axis, is known from DE 10 2009 053 679. The tube thread is generally manufactured at the tube end of the chucked tubular workpiece or tube for a one-time run-over of the tools commonly arranged in a turret head, the movements of the tools being controlled numerically. To chuck the tube, a machining apparatus has a front end chuck—where the turret head is employed with the tools—and a rear end chuck at the rear, both chucking the tube concentrically with respect to the rotation axis. A machining center with a minimum of two opposing machining apparatuses is equipped with four chucks. Both the front end chuck and the rear end chuck preferably have three jaw slides with jaws.
Such thread-cutting machines with a rotating tube and turret heads with fitted tools that are controlled via NC axes, require machining multiple chucking functions. The tubes must be able to be chucked compensating—first—centrally, with direct orientation toward the center of the machine, and—second—with adjustment to, thirdly, eccentrically chucked tubes. By external centered chucking is meant an additional chucking of the tube ends protruding from the front end chuck in the area of or close to the subsequently to be manufactured thread. This is accompanied by a compensating chucking by means of the jaw slides of the front end chucks if the jaw slides can be applied to the tube that is somewhat curved over the length, where applicable, in a compensating manner and thus not exactly centrally. Thus, such front end chucks are very complex and the chucking and releasing of the jaw slides or the jaws carried by them is implemented via wedge systems with rectangular redirection parallel to the center or rotation axis of the chuck, for the embodiment forms known in the field. This entails large diameters and lengths of the chucks with a respectively large mass, which is disadvantageous for operation.